<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>Document</title>
    <style>
    div{
    color:red;
    }
   #div1,#div2{
    color:blue;
   }
    </style>

</head>
<body>
<div id="div1"class="fun1">我是一个div1</div>
<div id="div2"class="fun">我是一个div2</div>
<div id="div3"class="fun1">我是一个div3</div>
</body>
</html>